ISCSI gets a boost from InfiniBand

According to the InfiniBand Trade Association (IBTA), the open-standards group charged with drafting the specifications for the 10/20 Gbps networking protocol,
InfiniBand will be coming soon to a storage environment near you.

The main reason for the IBTA's high hopes came in the form of an announcement on 25 September that a specification, known as iSER (iSCSI Extension for RDMA), has been ratified and will become part of the InfiniBand specification for connecting InfiniBand networks to iSCSI storage. RDMA stands for Remote Direct Memory Access, which allows the network adapter to transfer data directly to or from application memory, which is what makes InfiniBand so fast. ISER has also become part of the Linux 2.6.18 kernel and will be included in new versions of both SUSE and Red Hat Enterprise Linux.

What this ultimately means for storage users, according to proponents of iSER, is that iSCSI could soon become the choice over Fibre Channel (FC) in high-performance compute environments -- or even discriminating mainstream enterprise storage shops.

"The perception of iSCSI has been as a low-end, low-performance protocol," said Asaf Somekh, vice president (VP) of strategic alliances for Voltaire, a switching company that pioneered a FC-to-InfiniBand gateway two years ago. (Somekh also sits on the steering committee for IBTA.) "That's not iSCSI's fault. That's
Ethernet's fault."

According to IBTA, companies, including Silicon Graphics (SGI), Engenio Information Technologies and FalconStor Software are currently working on iSER products. Enterprise-focused vendors in switching and connectivity have also entered the market, at least nominally, through acquisition -- Cisco Systems by buying Topspin Communications in 2005 and QLogic with its acquisition of PathScale in 2006. Also, IBM and LSI Logic's Engenio subsidiary already offer FC-InfiniBand "hybrid" storage products.

One protocol for all?

The ultimate goal, according to Len Rosenthal, VP of marketing for QLogic and a marketing representative for IBTA, is to have InfiniBand become a standard protocol in the enterprise data center, using technology like Voltaire's gateway and iSER for iSCSI storage to unite FC, iSCSI and, in some cases, Ethernet under one umbrella.

Now that it's been ratified by IBTA over other RDMA specifications, such as Myrinet or Quadrics, iSER will be included in the OpenFabrics standard, which has just that unification in mind, Rosenthal said.

"We're hoping to see InfiniBand become a more viable alternative to both Ethernet and FC across multiple applications," Rosenthal said.

At the same time, Rosenthal admitted, users aren't just going to unplug their FC systems. For one thing, FC has been around for more than a decade now, while questions still remain for some in the industry as to the reliability of iSCSI storage.

"The big news for now is that there's an alternative, and it's gaining momentum," Rosenthal said.

So far, traction is slow but steady

For now, according to Somekh, the most immediate benefit of iSER is that it doesn't interfere with transporting data at the packet level, as opposed to other iSCSI-to-InfiniBand bridging protocols, such as IPoIB (IP over InfiniBand).

"Now you can take advantage of the speed of RDMA, but move things as one file at the megabyte level rather than fragmenting iSCSI over Ethernet or FCIP," he said.

So far, the IBTA estimates that traction for InfiniBand has been confined to high-performance computing environments, with around 500 end-user sites deploying InfiniBand products in clustering applications. Another limitation on InfiniBand's aspirations to enter the mainstream data center is that it is currently confined mostly to Linux operating systems, although Microsoft has announced its intentions to get into the high-performance computing space, and as of this past June, announced InfiniBand support in its Microsoft Cluster Compute Server (CCS) 2003 product.

"Infiniband is one of those promising technologies that is really exciting, [but] still needs to pass the test of meaningful customer adoption," said Christopher Baer, an account executive with storage services firm Broadleaf Services LLC, himself an iSCSI storage user as well as a storage service provider for EqualLogic Corp. and Riverbed Technology products.

On the other hand, Baer said, he has seen evidence that iSCSI is "really taking hold in a big way." Baer cited recent developments in the industry, including Microsoft's acquisition of iSCSI target maker String Bean Inc., VMware 's support for iSCSI in ESX 3.0 and the market penetration of IP SAN products, like EqualLogic's PS Series arrays.

"For customers that do implement Infiniband, it is smart that they be given the ability to port to an iSCSI storage array," Baer said. "In fact, I am sure that these customers would demand that connectivity between the tiers."

"IfiniBand sort of fell by the wayside for a while, but now it's back," said Arun Taneja, founder and senior analyst with the Taneja Group. This is good news, according to Taneja. "Even when it first came out, InfiniBand was the most complete spec I've ever seen. You can kick a spec like this in the teeth all you want, but you can't kill it."

Some in the industry have been working on a standard for RDMA with IP for years with nothing to show for it yet, Taneja said -- for now, iSER is filling that gap. "At some point, maybe we'll see it, but for now people have a job to do -- there are certain HPC [high-performance computing] applications that thrive on that functionality."

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